Phospholipids are a major component of all biological membranes. In its simplest form, a phospholipid is composed of glycerol bonded to two fatty acids and a phosphate group. Due to its polar nature, the head of a phospholipid is hydrophilic while the nonpolar tails are hydrophobic. When placed in water, phospholipids form a bilayer, composed of a hydrophobic core region formed by the acyl chains of the lipids, and hydrophilic membrane interfacial regions that are formed by the polar head groups of the lipids.
Membranes made of phospholipid bilayers are partially permeable, very flexible, and have fluid properties in which embedded proteins and phospholipid molecules are constantly moving laterally across the membrane. Proteins incorporated into the phospholipid bilayer can facilitate actions such as compartmentalization, passive and active transport, signal transduction, specific recognition, and energy utilization.
Because of their versatility in function, scientists have long sought to incorporate phospholipid bilayer membranes into artificial materials and devices. These devices have a broad range of potential applications including ligand based biosensors for clinical diagnostics; memory devices; screening devices for pharmaceutical applications; the provision of biologically functionalized surfaces; binding sites for small molecules such as drugs, pesticides, molecules required to be analyzed during process control (i.e. food stuffs, fermenter products, chemicals); larger molecules such as proteins for research screening (e.g. array technology) or diagnostics (cancer markers, infectious disease markers, hormones); nucleic acids; carbohydrate polymers; cells such as pathogenic bacteria; eukaryotic cells such a cancer cells and small single or multicellular organisms especially parasites; high throughput screening for pharmaceutical applications; controlled drug delivery; medical diagnosis; environmental monitoring, chemical and biological warfare agent sequestration; actuator development; power sources; electrochemical pumps; and bio-fuel cell development.
However, phospholipid bilayer membranes are inherently fragile. Due to their thinness, polar charge, tendency to naturally curve, and the inherently weak self-assembly forces at work, they are subject to disruption from phenomenon such as vibration, sonication, chemical reaction, pH, temperature denaturing, electromagnetic fields and the like making them unsuitable for applications outside of the most stringently controlled conditions. Additionally, it has been difficult to create membranes with uniform nanostructures capable of incorporating other proteins such as transmembrane proteins in nonrandom orientations.
There is therefore a need for the creation of stable membranes capable of mimicking natural biological processes. There is additionally a need for the creation of stable membranes which contain uniform nanostructures amenable to the incorporation of biomolecular complexes in nonrandom orientations.